Posted: 19/03/2016 at 08:32
I agree - closing yourself in with walls of dark evergreen would be worse than what you've got, making your garden and the rooms of your house dark and gloomy - the two trees you already have will screen well when in leaf, and at least in the winter they provide a 'filter' (a bit like a net curtain). Planting more trees would also impact badly on the growth of the trees you have.
The idea of providing visual interest to draw the eye into your garden is a really good one. It may also help to have a water feature that makes a sound, again to draw your attention inwards. In a few years you'll forget the warehouse is there.